url: speed up URLPattern

[anonrig]

This speeds up WHATWG URLPattern constructor, test(), and exec() without changing observable behavior.

Independent of the new URL() parse PR (nodejs#65361) and the URLSearchParams PR (nodejs#65363).

What changed

C++ only (src/node_url_pattern.cc):

• String input: copy one-byte ASCII V8 strings with ValueView + memcpy into a stack buffer and pass a string_view into Ada. Drop the extra std::string copy that BufferValue/Utf8Value::ToString() used to make. Non-ASCII still goes through Utf8Value.
• Object init: look up the nine interned component keys and assign fields by index. Skip UTF-8-converting each key name and the string-compare chain. Non-string members are still ignored.
• Regexp provider: convert pattern/input strings with ToV8Value and use isolate->GetCurrentContext() instead of Environment::GetCurrent.
• test / exec: share argument parsing so both paths keep the same WebIDL null/undefined/"null" baseURL behavior.

Ada still owns its parsed state; string_views only live for the duration of the C++ call. ValueView is destroyed before any V8 heap allocation.

Tests

• test/parallel/test-urlpattern.js, test-urlpattern-types.js, test-urlpattern-invalidthis.js, and test-urlpattern-fast-path.js all pass
• WPT test/wpt/test-urlpattern.js: 743 passed, 0 unexpected failures

Review follow-up

• Dropped the local NewStringFromUtf8View helper in favor of ToV8Value
• CopyV8StringToBuffer takes a pointer, matching project convention for mutating arguments
• Removed Signed-off-by from the commit (AI agents cannot attest DCO)